Conductivity Percolation of Carbon Nanotubes in Polyacrylamide Gels

Abstract

Polymer composites can be used in many different forms in various areas ranging from structural units in the construction industry to the composites of the aerospace applications. The extraordinary properties of carbon nanotubes make them very promising and favorable as fillers for fabrication of a new class of polymeric heterostructures. Polymer matrices have been widely exploited as a medium for carbonnanotubes (CNTs) which have been described as effective conducting fillers for polymers. Nanotubes can be described as long and slender fullerenes, in which the walls of the tubes are hexagonal carbon (graphite structure). There are two main types of carbon nanotubes (CNT) known as single (SWCNT) and multiwalled (MWCNT). Since the discovery of carbon nanotubes (CNT) in 1991 by lijima (lijima, 1991), singlewall carbon nanotubes (SWNT) and multiwalled carbon nanotubes (MWNT) have attracted great interests throughout the academic and industrial applications. Therefore, many researchers are focused on the development of CNT-based polymer materials that utilize the carbon nanotubes characteristics and properties, such as the high strength and stiffness of the CNTs are used for developing superior polymer composites for structural applications which are lighter, stronger, and tougher than any polymer-based material. There are several important requirements for an effective improvement of CNT-based composites’ properties, such as: a large aspect ratio of a filler, good exfoliation and dispersion of nanotubes, and good nanotube-nanotube and nanotube-polymer interfacial bonding. Numerous studies have shown already, that an effective performance of the carbon nanotubes in composites for a variety of applications strongly depends on the ability to disperse the CNTs homogenously throughout the matrix. Good interfacial bonding and interactions between nanotubes and polymers are also necessary conditions for improving mechanical properties of the composites. Because of their high mechanical strength, high aspect ratio, small diameter, light weight, high electrical and thermal conductivities, and high thermal and air stabilities, CNT have been found many applications in the industrial world (Chang, 2006; Hu, 2006). Polymer composites with carbon nanotube addition are one of the research subjects which attract huge attention in recent years (Lau, 2002& Thostenson, 2001). Thermoplastic polymers are usually used as an insulating material because of their low electrical conductivity properties (10-15 S/m). Dispersing the conducting filler such as carbon black and CNT in polymer phase forms conductive polymer composites. Electrical